Method for correcting a position error of lithography apparatus

ABSTRACT

A method for correcting a position error of a lithography apparatus comprises inputting position data of exposure pattern, irradiating laser light onto a position reference mask from a position measurement laser system, calculating actual position data of the laser light irradiated onto the position reference mask, and comparing the position data of the exposure pattern with the actual position data of the laser light irradiated onto the position reference mask. With this method, circuit patterns can be accurately formed at predetermined positions on a photomask, and the circuit patterns on the photomask can be accurately formed at predetermined positions on a wafer.

BACKGROUND

1. Field

Exemplary embodiments relate to a method for correcting a position errorof a lithography apparatus, and more specifically, to a method forcalculating a position error correction amount of a position referencemask to correct a position error of a lithography apparatus.

2. Description of the Related Art

In general, a photomask to be patterned is exposed to electron beamsirradiated from an electron-beam lithography apparatus. For example, alayer made of chrome or the like through which light is not transmittedis formed on a transparent glass substrate. A resist layer reacting toelectron beams or light may be formed on the layer made of chrome or thelike. Then, electron beams are irradiated to expose a shape which is tobe patterned. The resist layer is developed to form resist patterns. Thechrome layer is etched. The resist patterns are removed to complete thephotomask.

In this case, a process of irradiating the electron beams onto theresist layer may be the most important process.

However, the electron-beam lithography apparatus for manufacturing aphotomask as described above may have a position error due to the limitof accuracy in positioning a stage, mask sliding, and so on. Such aposition error tends to change according to time. Therefore, theposition error of the lithography apparatus needs to be correctedperiodically.

SUMMARY

Embodiments are therefore directed to a method for calculating aposition error correction amount of a position reference mask to correcta position error of a lithography apparatus, which substantiallyovercomes one or more of the problems due to the limitations anddisadvantages of the related art.

It is therefore a feature of an embodiment to provide a method forcorrecting a position error of a lithography apparatus, comprising:inputting position data of exposure pattern; irradiating laser lightonto a position reference mask from a position measurement laser system;calculating actual position data of the laser light irradiated onto theposition reference mask; and comparing the position data of the exposurepattern with the actual position data of the laser light irradiated ontothe position reference mask.

The method may further comprise calculating a position error correctionamount of the position reference mask based on a result of thecomparison when it is judged that a difference between the position dataof the exposure pattern and the actual position data of the laser lightis larger than a reference value.

The calculated position error correction amount may be equal to or lessthan the difference.

The method may further comprise moving a wafer stage on which a wafer isdisposed according to the calculated position error correction amount.

The method may further comprise irradiating laser light onto the waferfrom a light source after moving the wafer stage.

The position reference mask may be disposed on the wafer stage on whichthe wafer is disposed.

Irradiating the laser light onto the position reference mask may beperiodically performed while a resist disposed on the wafer is exposed.The position data of the exposure pattern and the actual position dataof the laser light irradiated onto the position reference mask may becompared and the position error correction amount of the positionreference mask is calculated. A position error of the wafer stage may becorrected in real time according to the calculated position errorcorrection amount.

The method may further comprise moving a mask stage on which a photomaskis disposed according to the calculated position error correctionamount.

The method may further comprise irradiating electron beams onto thephotomask after moving the mask stage.

The position reference mask may be disposed on the mask stage on whichthe photomask is disposed.

Irradiating the laser light onto the position reference mask may beperiodically performed while a resist disposed on the photomask isexposed. The position data of the exposure pattern and the actualposition data of the laser light irradiated onto the position referencemask may be compared and the position error correction amount of theposition reference mask is calculated. A position error of the maskstage may be corrected in real time according to the calculated positionerror correction amount.

The method may further comprise irradiating laser light onto a waferfrom a light source when it is judged that a difference between theposition data of the exposure pattern and the actual position data issmaller than a reference value.

The method may further comprise irradiating electron beams onto aphotomask, when it is judged that a difference between the position dataof the exposure pattern and the actual position data is smaller than areference value.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other features and advantages will become more apparent tothose of ordinary skill in the art by describing in detail exemplaryembodiments with reference to the attached drawings, in which:

FIG. 1 illustrates a diagram of a grid map for explaining a positionerror of an electron-beam lithography apparatus.

FIG. 2 illustrates a graph presenting changes in a position error of anelectron-beam lithography apparatus according to time.

FIG. 3 illustrates a schematic view of an electron-beam lithographyapparatus according to an exemplary embodiment.

FIGS. 4A and 4B illustrate diagrams for explaining a process ofcalculating a position error correction amount using a positionreference mask according to an exemplary embodiment.

FIG. 5 illustrates a flow chart of a method for correcting a positionerror of the electron beam lithography apparatus according to anexemplary embodiment.

FIGS. 6A to 6C illustrate schematic cross-sectional views for explaininga process of forming a photomask.

FIG. 7A illustrates a schematic diagram for explaining a process ofcalculating position data using a profile of received laser light.

FIG. 7B illustrate the profile obtained by inverting an intensity oflaser light reflected from the position reference mask.

FIG. 8 illustrates a schematic view of a wafer-processing lithographyapparatus according to an exemplary embodiment.

FIG. 9 illustrates a flow chart of a method for correcting a positionerror of the wafer-processing lithography apparatus according to anexemplary embodiment.

DETAILED DESCRIPTION

Korean Patent Application No. 10-2009-0013433, filed on Feb. 18, 2009,in the Korean Intellectual Property Office, and entitled: “Method forCorrecting a Position Error of Lithography Apparatus,” is incorporatedby reference herein in its entirety.

In the drawing figures, the dimensions of layers and regions may beexaggerated for clarity of illustration. It will also be understood thatwhen a layer or element is referred to as being “on” another layer orsubstrate, it can be directly on the other layer or substrate, orintervening layers may also be present. In addition, it will also beunderstood that when a layer is referred to as being “between” twolayers, it can be the only layer between the two layers, or one or moreintervening layers may also be present. Like reference numerals refer tolike elements throughout.

Various exemplary embodiments will now be described more fully withreference to the accompanying drawings in which some exemplaryembodiments are shown. In the drawings, the thicknesses of layers andregions may be exaggerated for clarity.

Accordingly, while exemplary embodiments are capable of variousmodifications and alternative forms, embodiments thereof are shown byway of example in the drawings and will herein be described in detail.It should be understood, however, that there is no intent to limitexemplary embodiments to the particular forms disclosed, but on thecontrary, exemplary embodiments are to cover all modifications,equivalents, and alternatives falling within the scope of the invention.Like numbers refer to like elements throughout the description of thefigures.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of exemplaryembodiments. As used herein, the singular forms “a,” “an” and “the” areintended to include the plural forms as well, unless the context clearlyindicates otherwise. It will be further understood that the terms“comprises,” “comprising,” “includes” and/or “including,” when usedherein, specify the presence of stated features, integers, steps,operations, elements and/or components, but do not preclude the presenceor addition of one or more other features, integers, steps, operations,elements, components and/or groups thereof.

Exemplary embodiments are described herein with reference tocross-sectional illustrations that are schematic illustrations ofidealized embodiments (and intermediate structures). As such, variationsfrom the shapes of the illustrations as a result, for example, ofmanufacturing techniques and/or tolerances, may be expected. Thus,exemplary embodiments should not be construed as limited to theparticular shapes of regions illustrated herein but may includedeviations in shapes that result, for example, from manufacturing. Thus,the regions illustrated in the figures are schematic in nature and theirshapes do not necessarily illustrate the actual shape of a region of adevice and do not limit the scope.

It should also be noted that in some alternative implementations, thefunctions/acts noted may occur out of the order noted in the figures.For example, two figures shown in succession may in fact be executedsubstantially concurrently or may sometimes be executed in the reverseorder, depending upon the functionality/acts involved.

In order to more specifically describe exemplary embodiments, variousaspects will be described in detail with reference to the attacheddrawings. However, the invention is not limited to exemplary embodimentsdescribed.

FIG. 1 illustrates a diagram of a grid map for explaining a positionerror of an electron-beam lithography apparatus.

Referring to FIG. 1, an electron-beam lithography apparatus may have aposition error as shown in FIG. 1 due to the limit of accuracy inpositioning a stage, mask sliding, and so on.

That is, in the electron-beam lithography apparatus for manufacturing aphotomask, an electron-beam irradiation system may irradiate electronbeams to a predetermined position, while a stage having a photomaskseated thereon moves in four directions. The electron beams areirradiated onto the surface of the photomask to form patterns. However,a position error of the lithography apparatus may be caused by the limitof accuracy in positioning the stage, mask sliding, and so on.Therefore, as illustrated in FIG. 1, electron beams to be irradiatedonto a position A on the photomask may be irradiated on to a positionA′.

FIG. 2 illustrates a graph presenting changes in a position error of anelectron-beam lithography apparatus according to time.

Referring to FIG. 2, a position to which an electron beam is to beirradiated is set to T, and a grid position of the actually-irradiatedelectron beam is represented by X or Y. As shown in FIG. 2, the gridposition X and Y of the actually-irradiated electron beam changes fromthe position T according to time.

The above-described position error may be corrected in real time by anelectron-beam lithography apparatus as described below.

FIG. 3 illustrates a schematic view of an electron-beam lithographyapparatus according to an exemplary embodiment.

Referring to FIG. 3, an electron beam lithography apparatus 100 mayinclude an electron gun 111 configured to emit electron beams 111 a, anelectronic lens unit 112 configured to guide the emitted electron beamsin one direction, and an aperture 113 configured to adjust the size ofthe electron beams.

The electron gun 111 may receive electric energy to emit electronsthrough heat emission or field emission. Further, the electron lens unit112 may provide a magnetic field so as to guide electron beams emittedfrom the electron gun 111 in one direction.

The electronic lens unit may include a shaping deflector configured toshape electron beams into a predetermined shape, a shaping lens, and anobject lens configured to condense the electron beams, depending on adesign of the electronic lens unit. The configuration of the electroniclens unit is not limited to this embodiment.

The aperture 113 may serve to adjust the size of electron beams. Theaperture 113 may be formed in a variable rectangular shape. In thiscase, blinds of the aperture may adjust the size of an opening throughwhich electron beams may pass, in order to adjust the size of theelectron beams. Further, the aperture 113 may be formed in a circularshape. In this case, blinds of the aperture may rotate to adjust thesize of an opening through which electron beams may pass in order toadjust the size of the electron beams. The shape of the aperture is notlimited to the above-described shapes.

A mask stage 130 may be disposed having a predetermined distance fromthe aperture. A photomask 120 may be disposed on the mask stage 130.

In this case, the mask stage 130 may comprise an X-axis mask stage 130 aand a Y-axis mask stage 130 b. The X-axis mask stage 130 a may move thephotomask along the X-axis. The Y-axis stage 130 b may move thephotomask along the Y-axis.

Further, a resist may be applied onto the photomask 120. The photomaskmay be formed through the resist as follows.

FIGS. 6A to 6C illustrate schematic cross-sectional views for explaininga process of forming a photomask.

Referring to FIG. 6A, the photomask may include a light shielding layer120 b formed on a substrate 120 a and a resist layer 120 c formed on thelight shielding layer 120 b. The substrate 120 a may be a glasssubstrate made of quartz.

The light shielding layer 120 b may be a chrome layer for shieldinglight. The light shielding layer 120 b may be made of material that hasan excellent adhesive force with the glass substrate 120 a and a similarthermal expansion coefficient to that of the glass substrate 120 a, andcan reflect light. That is, metallic materials may be used as materialfor the light shielding layer 120 b. In addition to chrome, metalsincluding aluminum, titanium, molybdenum, ruthenium, tantalum, and soon, metal alloys, or a metal compound combined with oxygen or nitrogenmay be used as material for the light shielding layer 120 b. Forexample, a chrome-aluminum alloy, chrome oxide, chrome nitride, aluminumoxide, aluminum nitride, oxides and nitrides of other metals, orcompounds such as oxynitrides of all metals may be used as material forthe light shielding layer 120 b.

Although not illustrated in FIGS. 6A to 6C, an anti-reflection layer maybe formed on the light shielding layer 120 a. Any layer which reflects asmall amount of light than the light shielding layer 120 a may bedesignated as the anti-reflection layer. The anti-reflection layer maybe formed as an independent material layer. However, the anti-reflectionlayer may be formed of a material layer which can be patterned at thesame time as the light shielding layer 120 a, considering easiness ofpattern formation. For example, when the light shielding layer 120 a isformed of a chrome layer, a chrome oxide layer may be formed as theanti-reflection layer. Even when the light shielding layer 120 a is nota pure chrome layer but made of a metal alloy or metal compoundcontaining chrome, the chrome oxide layer may be used as theanti-reflection layer.

The resist layer 120 c may be made of material which can be selectivelypatterned by a developing solution after being exposed to electronbeams. Specifically, the resist layer 120 c may be made of a highlypolymerized compound based on carbon. The resist layer 120 c may be anelectron beam resist layer.

The resist layer 120 c may be exposed to the electron beams irradiatedonto the above-described photomask, and then developed by a developingsolution to form resist patterns 120 c′ as illustrated in FIG. 6B.Specifically, to form the resist patterns 120 c′, the developingsolution may be jetted or poured onto the surface of the resist layer120 c. Alternatively, the photomask may be dipped in the developingsolution. When the resist patterns 120 c′ are formed, the lightshielding layer 120 b under the resist patterns 120 c′ may beselectively exposed. Since developing methods are well-known techniques,the detailed descriptions of the development methods are omitted here.

Referring to FIG. 6C, the exposed light shielding layer 120 b may beetched using the resist patterns 120 c′ as an etching mask in order toform light shielding patterns 120 b′ through which the substrate 120 ais selectively exposed. Specifically, the exposed light shielding layer120 b may be etched with a wet or dry etching method to form the lightshielding patterns 120 b′ through which the substrate 120 a isselectively exposed. In the wet etching method, the photomask may bedipped in an acid etching solution, or the etching solution may bejetted onto the surface of the light shielding layer 120 b. The acidetching solution may include H₂SO₄, HF, H₂PO₄, or HCl. In the dryetching method, a combination of etching gases including halogen groupgases (F, Cl, Br, and so on) may be used. The gases including halogengroup gases may be CF₄, CHF₃, C₂F₄, C₃F₄, C₃F₆, C₄F₈, SF₆, or CCl₄. Thecombination of etching gases may include the gases including halogengroup gases and inert gases such as Ne, Ar, and Xe. Further, thecombination of etching gases may include one or more of O₂ and N₂. Sinceetching methods are well-known techniques, the detailed descriptions ofthe etching methods are omitted here.

After that, the resist patterns 120 c′ may be removed to selectivelyexpose the light shielding patterns 120 b′ and the substrate 120 a.Consequently, a photomask having final circuit patterns may be formed.At this time, the resist patterns 120 c′ may be removed with a wetmethod using a stripper containing H₂SO₄ or a dry method using acombination of gases containing O₂.

Returning to FIG. 3, the electron beam lithography apparatus accordingto an exemplary embodiment will be described.

The lithography apparatus may further include a position measurementlaser system 114 and a position reference mask 115. The positionmeasurement laser system 114 and the electron gun 111 may be installedon a mount 110. The position reference mask 115 may be disposed at aposition having a predetermined distance from the position measurementlaser system 114. In this case, the position reference mask 115 may bedisposed on the mask stage on which the photomask is disposed.

The position measurement laser system 114 may irradiate laser light ontoa position reference mask 115 to calculate the position of theirradiated laser light. The position reference mask 115 may have areference grid formed thereon. The actual position of the laser lightirradiated from the position measurement laser system 114 may becompared with a position of the reference grid.

As described above, the position reference mask 115 may be disposed onthe mask stage on which the photomask is disposed. Therefore, when thephotomask moves, the position reference mask 115 may move for the samedistance as the photomask 120.

That is, the position reference mask 115 and the photomask 120simultaneously move for the same distance. Therefore, the position ofthe photomask 120 may be calculated by calculating the position of theposition reference mask 115.

Further, when a position error occurs on the position reference mask115, the same position error may occur on the photomask 120. Therefore,it may be possible to calculate the position error of the photomask 120.In particular, since the position of the position reference mask 115 maybe periodically calculated even while the photomask 120 is exposed, theposition error of the photomask 120 may be calculated in real time.

FIGS. 4A and 4B illustrate diagrams for explaining a process ofcalculating a position error correction amount using a positionreference mask according to an exemplary embodiment.

Referring to FIG. 4A, the position reference mask may include asolid-line reference grid. The solid-line reference grid may protrudefrom the surface of the position reference mask.

A position of the reference grid may be represented by x and y. In thiscase, a position to which laser light is to be irradiated from theposition measurement laser system may be set to T₁(x₁, y₁), and theposition of actually-irradiated laser light may be determined as P₁(x₁′,y₁′). That is, a position error corresponding to a difference betweenP₁(x₁′, y₁′) and T₁(x₁, y₁) may occur.

Therefore, the difference between P₁(x₁′, y₁′), which is the position ofthe actually-irradiated laser light, and T₁(x₁, y₁), to which laserlight is to be irradiated from the position measurement laser system,may correspond to a position error correction amount.

Referring to FIG. 4B, the position reference mask may include across-shaped reference grid. The cross-shaped reference grid mayprotrude from the surface of the position reference mask.

A position of the reference grid may be represented by x and y. In thiscase, a position to which laser light is to be irradiated from theposition measurement laser system may be set to T₂(x₂, y₂), and theposition of actually-irradiated laser light may be determined as P₂(x₂′,y₂′). That is, a position error corresponding to a difference betweenP₂(x₂′, y₂′) and T₂(x₂, y₂) may occur.

Therefore, the difference between P₂(x₂′, y₂′), which is the position ofthe actually-irradiated laser light, and T₂(x₂, y₂), to which laserlight is to be irradiated from the position measurement laser system,may correspond to a position error correction amount.

As described above, the position reference mask and the photomask maysimultaneously move for the same distance. Therefore, when a positionerror occurs on the reference position mask, the same position error mayoccur on the photomask. Accordingly, it may be possible to calculate aposition error correction amount of the photomask by using the positionerror correction amount of the position reference mask.

FIG. 5 illustrates a flow chart of a method for correcting a positionerror of the electron beam lithography apparatus according to anexemplary embodiment.

Referring to FIG. 5, position data of exposure patterns to be formed onthe photomask may be input in operation S101. At this time, as electronbeams may be irradiated according to the position data of the exposurepattern to expose the resist disposed on the photomask, resist patternsmay be formed. Further, the position data of the exposure pattern mayalso be applied to the position measurement laser system. In this case,as laser light is periodically irradiated onto the position referencemask according to the position data, a position of the positionreference mask may be periodically calculated even during the resistexposure. Therefore, it may be possible to calculate the position of thephotomask.

Next, as shown in FIG. 5, in operation S102, the position measurementlaser system may irradiate laser light onto the position reference mask.In operation S103, actual position data of the laser light irradiatedonto the position reference mask may be calculated.

At this time, laser light may be irradiated onto the position referencemask from the position measurement laser system before the electronbeams are irradiated onto the photomask.

That is, before the electron beams are irradiated in order to expose theresist disposed on the photomask such that the resist patterns areformed, the position measurement laser system may irradiate laser lightonto the position reference mask to calculate a position errorcorrection amount of the position reference mask. Further, the positionerror of the photomask having the resist applied thereon may becorrected by using the position error correction amount of the positionreference mask. Therefore, the circuit patterns may be accurately formedat predetermined positions on the photomask.

Laser light may be irradiated onto the position reference mask from theposition measurement laser system periodically even while the resist isexposed. Therefore, even when a position error occurs during the resistexposure, the position error of the photomask having the resist appliedthereon may be corrected in real time by using the position errorcorrection amount of the position reference mask.

At this time, the actual position data of the laser light irradiatedonto the position reference mask may be calculated by the followingprocess.

FIG. 7A illustrates a schematic diagram for explaining a process ofcalculating position data using a profile of received laser light. FIG.7B illustrate the profile obtained by inverting an intensity of laserlight reflected from the position reference mask.

Referring to FIG. 7A, when laser light is irradiated onto a positionreference mask having a protrusion-shaped reference grid 115 a,reflected laser light may be received. The irradiated laser light maynot be reflected but scattered at the edges of the protrusion-shapedreference grid 115 a. In such a case, an intensity of the laser lightreceived from the edges may be low. Accordingly, it may be possible toobtain a profile as illustrated in FIG. 7B by inverting the intensity ofthe received laser light.

Specifically, the inverted intensity of laser light may reach the peakat the edges of the reference grid. Such a peak may be analyzed tocalculate the actual position data of the laser light. Positionmeasurement methods are well-known techniques. Therefore, the detaileddescriptions of the position measurement methods are omitted here.

Returning to FIG. 5, the pattern position data may be compared with theactual position data of laser light in operation S104.

That is, the position data of the exposure pattern input in operation101 may be compared with the actual position data of the laser lightirradiated onto the position reference mask. The actual position datamay be calculated in operation S103. Then, it can be judged whether adifference between the data is acceptable or not.

When it is judged through the comparison that the difference between thedata is acceptable, that is, the amount of the position error of theposition reference mask is smaller, the process may proceed to operationS107. In operation S107, electron beams may be irradiated onto thephotomask to expose the resist on the photomask.

On the other hand, when it is judged through the comparison that thedifference between the data is unacceptable, that is, the amount of theposition error of the position reference mask is larger, the process mayproceed to operation 105. In operation 105, a position error correctionamount of the position reference mask may be calculated.

At this time, whether the difference between the data is acceptable orunacceptable may be set by an operator who performs the process. Thereference value may be properly determined depending on the processes.

As described above, when the difference between the data is acceptable,electron beams may be irradiated onto the photomask to expose the resiston the photomask in operation S107 shown in FIG. 5. Then, the method ofcorrecting a position error of the lithography apparatus may becompleted.

However, when the difference between the data is unacceptable, theposition error correction amount of the position reference mask may becalculated in operation S105 shown in FIG. 5. The mask stage may bemoved according to the calculated correction amount in operation S106shown in FIG. 5.

For example, as shown in FIG. 4A, when the position to which laser lightis to be irradiated from the position measurement laser system, theinput pattern position data has been set to T₁(x₁, y₁), but the actualposition of the irradiated laser light may be P₁(x₁′, y₁′). In thiscase, a position error corresponding to a difference between P₁(x₁′,y₁′) and T₁(x₁, y₁) may occur. Therefore, a correction amount C may becalculated to be (x₁′-x₁, y₁′-y₁). According to the calculatedcorrection amount, the X-axis mask stage may be moved for as much asx₁′-x₁ along the X-axis, and the Y-axis mask stage may be moved for asmuch as y₁′-y₁ along the Y-axis. Thus, the position error of thephotomask having the resist applied thereon may be corrected.

Next, electron beams may be irradiated onto the photomask to expose theresist on the photomask in operation S107 shown in FIG. 5. Then, theposition error correction method of the lithography apparatus may becompleted.

Additionally, the technical idea of the inventive concept may be appliedto a wafer processing process for manufacturing semiconductor devices aswell as the photomask manufacturing process. When the technical idea isapplied to the wafer processing process, the above-described photomaskmay be a wafer, and the mask stage may be a wafer stage. An exemplaryembodiment is described in detail as follows.

FIG. 8 illustrates a schematic view of a wafer-processing lithographyapparatus according to an exemplary embodiment.

Referring to FIG. 8, a wafer-processing lithography apparatus 200 mayinclude a light source 211 and an illumination optical system 212disposed at a position having a predetermined distance from the lightsource 211. In this case, the light source may be installed on a mount210.

The light source 211 may irradiate light to the illumination opticalsystem 212. As the light source 211, KrF excimer laser having awavelength of 248 nm or ArF excimer laser having a wavelength of 193 nmmay be used. However, the type of the light source is not limited tothose light sources.

The illumination optical system 212 may include a neutral density (ND)filter, a lens unit, a masking blade, and so on. The ND filter 212 a mayserve to reduce an amount of light incident from the light source 211 toadjust an intensity of the light. The illumination optical system 212may prevent occurrence of diffraction. The lens unit 212 b may be a lensarray including an input lens, a condenser lens, a fly eye lens, and soon. The condenser lens may serve to condense light incident to the lensunit 212 b to form parallel beams. The fly eye lens may serve touniformly adjust illumination of light incident to the lens unit 212 b.The masking blade 212 c may serve to define an irradiation region of thelight passing through the illumination optical system 212. Theillumination optical system 212 may further include a mirror portion.

A photomask 213 may be disposed at a position having a predetermineddistance from the illumination optical system 212. The photomask 213 mayinclude exposure patterns identical to circuit patterns which are to beformed on a wafer 223.

For example, the photomask 213 may include a transparent substrate.Light shielding pattern regions may be arranged on the transparentsubstrate. The transparent substrate may be made of transparent quartz.On the light shielding pattern regions, exposure patterns to bedeposited on the transparent substrate, for example, chrome layerpatterns, may be disposed.

That is, the photomask 213 may be formed by the above-describedelectron-beam lithography apparatus.

The photomask 213 may be positioned on a mask stage 220. The mask stage220 may comprise an X-axis mask stage 220 a and a Y-axis mask stage 220b.

The X-axis mask stage 220 a may move the photomask 213 along the X-axis.The Y-axis mask stage 220 b may move the photomask 213 along the Y-axis.

A projection optical system 221 may be disposed at a position having apredetermined distance from the photomask 213. The projection opticalsystem 221 may be a reduction projection optical system. The projectionoptical system 221 may include a lens array.

A wafer stage 230 may be disposed at a position having a predetermineddistance from the projection optical system 221. A wafer 223 may bedisposed on the wafer stage 230.

The wafer stage 230 may comprise an X-axis wafer stage 230 a and aY-axis wafer stage 230 b. The X-axis wafer stage 230 a may move thewafer 223 along the X-axis. The Y-axis wafer stage 230 b may move thewafer 223 along the Y-axis.

A resist 222 may be applied onto the wafer 223. The resist 222 may be acomponent for forming circuit patterns on the wafer 223. Since this isobvious to those skilled in the art, detailed description of the resist222 is omitted here.

Continuously, referring to FIG. 8, the wafer-processing lithographyapparatus 200 according to the exemplary embodiment is described asfollows.

The wafer-processing lithography apparatus 200 may include a positionmeasurement laser system 214 and a position reference mask 215. Theposition measurement laser system 214 may be installed on a mount 210 onwhich the light source is installed. The position reference mask 215 maybe disposed at a position having a predetermined distance from theposition measurement laser system 214. The position reference mask 215may be disposed on the wafer stage 230 on which the wafer 223 isdisposed.

The position measurement laser system 214 may irradiate laser light ontothe position reference mask 215 to calculate the position of theirradiated laser light. The position reference mask 215 may have areference grid formed thereon to compare the actual position of laserlight irradiated from the position measurement laser system 214 with thepattern position data.

As described above, the position reference mask 215 may be disposed onthe wafer stage 230 on which the wafer 223 is disposed. Therefore, whenthe wafer 223 having the resist 222 applied thereon moves, the positionreference mask 215 may move for the same distance as the wafer 223having the resist 222 applied thereon.

That is, the position reference mask 215 and the wafer 223 having theresist 222 applied thereon may move for the same distancesimultaneously. Therefore, the position of the wafer 223 having theresist 222 applied thereon may also be calculated by calculating theposition of the position reference mask 215.

Further, when a position error occurs on the position reference mask215, the same position error may occur on the wafer 223 having theresist 222 applied thereon. Therefore, it may be possible to calculatethe position error of the wafer 223 having the resist 222 appliedthereon. In particular, as the position of the position reference mask215 is periodically calculated even during the resist exposure, theposition error of the wafer 223 may be calculated in real time.

A position error correction amount using the position reference mask maybe calculated in the same manner as in the electron-beam lithographyapparatus. Therefore, the description of the calculation is omittedhere.

FIG. 9 is a flow chart of a method for correcting a position error ofthe wafer-processing lithography apparatus according to an exemplaryembodiment.

Referring to FIG. 9, a position data of exposure patterns of a photomaskmay be input in operation S201. The exposure patterns are identical tocircuit patters to be formed on the above-described wafer. At this time,according to the position data of the exposure pattern, the light sourcemay irradiate laser light to expose the resist disposed on the wafer soas to form resist patterns. Further, the position data of the exposurepattern may be applied to the position measurement laser system. In thiscase, as laser light is periodically irradiated onto the positionreference mask according to the position data, the position of theposition reference mask may be periodically calculated even during theresist exposure. Accordingly, it may be possible to calculate theposition of the wafer having the resist applied thereon.

Next, the position measurement laser system may irradiate laser lightonto the position reference mask in operation S202 shown in FIG. 9.Actual position data of the laser light irradiated onto the positionreference mask may be calculated in operation S203.

At this time, laser light onto the position reference mask from theposition measurement laser system may be irradiated before the lightsource irradiates laser light.

That is, before the light source irradiates laser light in order toexpose the resist on the wafer so as to form the resist patterns, theposition measurement laser system may irradiate laser light onto theposition reference mask to calculate a position error correction amountof the position reference mask. Then, the position error of the waferhaving the resist applied thereon may be corrected using the positionerror correction amount of the position reference mask. Therefore, thecircuit patterns defined on the photomask may be accurately formed atpredetermined positions on the wafer.

Further, laser light onto the position reference mask from the positionmeasurement laser system may be periodically irradiated even while theresist is exposed. Therefore, when a position error occurs during theresist exposure, the position error of the wafer having the resistapplied thereon may be corrected in real time by using the positionerror correction amount of the position reference mask.

The actual position data of the laser light irradiated onto the positionreference mask may be calculated in the same manner as in theelectron-beam lithography apparatus. Therefore, description of thecalculation is omitted here.

Next, the pattern position data may be compared with the actual positiondata of the laser light in operation S204 shown in FIG. 9.

That is, the exposure pattern position data input in operation S201 maybe compared with the actual position data of the laser light irradiatedonto the position reference mask. The actual position data is calculatedin operation S203. Then, it may be judged whether a difference betweenthe data is acceptable or not.

When it is judged from the comparison that the difference between thedata is acceptable, that is, when the amount of position error of theposition reference mask is smaller, the process may proceed to operationS207 shown in FIG. 9. In operation S207, the light source irradiateslaser light onto the wafer such that the circuit patterns defined on thephotomask are formed at predetermined positions of the wafer.

Further, when it is judged from the comparison that the differencebetween the data is unacceptable, that is, when the amount of positionerror of the position reference mask is larger, the process may proceedto operation S205 shown in FIG. 9. In operation S205, a position errorcorrection amount of the position reference mask is calculated.

At this time, whether the difference between the data is acceptable orunacceptable may be set by an operator who performs the process. Thereference value may be properly determined depending on processes.

As described above, when the difference between the data is acceptable,the light source may irradiate laser light onto the wafer in operationS207 shown in FIG. 9 so as to form the circuit patterns defined on thephotomask at predetermined positions on the wafer. Then, the method forcorrecting a position error of the wafer-processing lithographyapparatus may be completed.

However, when the difference between the data is unacceptable, aposition error correction amount of the position reference mask may becalculated in operation S205 shown in FIG. 9. The wafer stage may bemoved according to the calculated correction amount in operation S206shown in FIG. 9.

The wafer stage may be moved according to the calculated correctionamount in the same manner as in the electron-beam lithography apparatusaccording to the exemplary embodiment. Therefore, description ofmovement of the wafer stage is omitted here.

Next, the light source may irradiate laser light onto the wafer inoperation S207 shown in FIG. 9 so as to form the circuit patternsdefined on the photomask at predetermined positions on the wafer. Then,the method for correcting a position error of the wafer-processinglithography apparatus may be completed.

When the circuit patterns of the photomask are formed by the lithographyapparatus, the position reference mask may be disposed on the mask stageon which the photomask is disposed. Therefore, the circuit patterns maybe accurately formed at predetermined positions on the photomask.Further, as the position error correction amount of the positionreference mask is periodically calculated, it may be possible to correctthe position error of the photomask having the resist applied thereon inreal time.

Further, when the circuit patterns of the photomask are transferred ontothe wafer by the lithography apparatus, the position reference mask maybe disposed on the wafer stage on which the wafer is disposed.Therefore, the circuit patterns defined on the photomask may beaccurately formed at predetermined positions on the wafer. Further, asthe position error correction amount of the position reference mask isperiodically calculated, it may be possible to correct the positionerror of the wafer having the resist applied thereon in real time.

The foregoing is illustrative of exemplary embodiments and is not to beconstrued as limiting thereof. Although several exemplary embodimentshave been described, those skilled in the art will readily appreciatethat many modifications are possible in the exemplary embodimentswithout materially departing from the novel teachings and advantages.Accordingly, all such modifications are intended to be included withinthe scope of the invention as defined in the claims. In the claims,means-plus-function clauses, if any, are intended to cover not only thestructures described herein as performing the recited function, but alsostructural equivalents. Therefore, it is to be understood that theforegoing is illustrative of various exemplary embodiments and is not tobe construed as limited to the specific embodiments disclosed, and thatmodifications to the disclosed embodiments, as well as otherembodiments, are intended to be included within the scope of theappended claims.

1. A method for correcting a position error of a lithography apparatus,comprising: inputting position data of exposure pattern; irradiatinglaser light onto a position reference mask from a position measurementlaser system; calculating actual position data of the laser lightirradiated onto the position reference mask; and comparing the positiondata of the exposure pattern with the actual position data of the laserlight irradiated onto the position reference mask.
 2. The method asclaimed in claim 1, further comprising calculating a position errorcorrection amount of the position reference mask based on a result ofthe comparison when it is judged that a difference between the positiondata of the exposure pattern and the actual position data of the laserlight is larger than a reference value.
 3. The method as claimed inclaim 2, wherein the calculated position error correction amount isequal to or less than the difference.
 4. The method as claimed in claim2, further comprising moving a wafer stage on which a wafer is disposedaccording to the calculated position error correction amount.
 5. Themethod as claimed in claim 4, further comprising irradiating laser lightonto the wafer from a light source after moving the wafer stage.
 6. Themethod as claimed in claim 4, wherein the position reference mask isdisposed on the wafer stage on which the wafer is disposed.
 7. Themethod as claimed in claim 4, wherein irradiating the laser light ontothe position reference mask is periodically performed while a resistdisposed on the wafer is exposed, the position data of the exposurepattern and the actual position data of the laser light irradiated ontothe position reference mask are compared and the position errorcorrection amount of the position reference mask is calculated, and aposition error of the wafer stage is corrected in real time according tothe calculated position error correction amount.
 8. The method asclaimed in claim 2, further comprising moving a mask stage on which aphotomask is disposed according to the calculated position errorcorrection amount.
 9. The method as claimed in claim 8, furthercomprising irradiating electron beams onto the photomask after movingthe mask stage.
 10. The method as claimed in claim 8, wherein theposition reference mask is disposed on the mask stage on which thephotomask is disposed.
 11. The method as claimed in claim 8, whereinirradiating the laser light onto the position reference mask isperiodically performed while a resist disposed on the photomask isexposed, the position data of the exposure pattern and the actualposition data of the laser light irradiated onto the position referencemask are compared and the position error correction amount of theposition reference mask is calculated, and a position error of the maskstage is corrected in real time according to the calculated positionerror correction amount.
 12. The method as claimed in claim 1, furthercomprising irradiating laser light onto a wafer from a light source whenit is judged that a difference between the position data of the exposurepattern and the actual position data is smaller than a reference value.13. The method as claimed in claim 1, further comprising irradiatingelectron beams onto a photomask, when it is judged that a differencebetween the position data of the exposure pattern and the actualposition data is smaller than a reference value.
 14. A method forcorrecting a position error of a lithography apparatus, comprising:inputting a position data T₁(x₁, y₁) of an exposure pattern; irradiatinglaser light onto a position reference mask installed on the stage from aposition measurement laser system installed on a mount; calculating anactual position data P₁(x₁′, y₁′) of the laser light irradiated onto theposition reference mask; comparing the position data T1(x1, y1) with theactual position data P1(x1′, y1′); judging through the comparisonwhether a difference between the data is acceptable or not; calculatinga position error correction amount of the position reference mask basedon a result of the comparison when it is judged that the differencebetween the data is unacceptable; and moving the stage according to thecalculated position error correction amount.
 15. The method as claimedin claim 14, further comprising irradiating laser light onto a waferinstalled on the stage from a light source installed on the mount aftermoving the stage.
 16. The method as claimed in claim 14, furthercomprising irradiating laser light onto a photomask installed on thestage from a light source installed on the mount after moving the stage.17. The method as claimed in claim 14, wherein it is judged that thedifference between the data is unacceptable if it is judged that thedifference between the data is larger than a reference value.